1. Field of the Invention
The invention relates generally to a multiple directional clutch for a vertical axis washing machine and more specifically to a multiple directional wrap spring clutch that enables dynamic breaking of a washing machine basket.
2. Description of the Related Art
Vertical axis washing machines typically comprise an agitator, impeller, or other clothes and/or wash liquid moving element mounted for rotation inside a perforated basket, which defines a wash chamber for holding a clothes load and is rotationally mounted inside a stationary wash tub. During a wash cycle, the clothes load is usually subjected to a wash step to wash the clothes load with wash liquid, a rinse step to rinse the wash liquid from the clothes load with water, and a spin step to extract excess rinse water from the clothes load. During the wash and rinse steps, the agitator rotates relative to the basket to move the clothes load and/or liquid within the wash chamber. During the spin step, both the agitator and the basket typically rotate at high speeds in the same direction to plaster the clothes load against the peripheral wall of the basket and thereby extract excess water from the items in the clothes load.
Rotation of the agitator and the basket is driven by a motor located in the washing machine beneath the wash tub. The agitator is fixedly mounted to an upper end of an agitator shaft that extends through the bottom of the basket, and the lower end of the agitator shaft is coupled to the motor such that the motor applies torque to the agitator shaft to induce rotation of the agitator shaft and thereby the agitator. Usually, the motor is reversible to reverse the rotational direction of the agitator according to stage of the wash cycle. Additionally, the motor dynamically brakes the agitator by reversing the torque applied to the agitator from its current rotational direction.
The basket is fixedly attached to a spin tube that surrounds the agitator shaft with upper and lower bushings therebetween. The spin tube is selectively mechanically coupled to the agitator shaft via a unidirectional clutch mechanism. When the clutch mechanism mechanically couples the spin tube to the agitator shaft, the spin tube rotates with the agitator shaft so both the basket and the agitator rotate together. Conversely, when the clutch mechanism mechanically decouples the spin tube from the agitator shaft, the agitator rotates alone while the basket remains stationary. To cease rotation of the spin tube and thereby the basket, the washing machine includes a separate mechanical brake mechanism that engages the spin tube or other component coupled to the basket when commanded to do so by a controller.
Numerous types of clutch mechanisms have been developed to accomplish transmission of rotational energy from the agitator shaft to the spin tube. One type of well-known clutch mechanism is a wrap spring clutch. Typically, a wrap spring clutch is a torsion spring disposed around the outer diameter of the spin tube and a coupler integrally formed with or otherwise fixed to the agitator shaft and axially aligned with the spin tube. Commonly, the wrap spring is wrapped around spin tube and the coupler so that in its neutral state, it is in a tightened condition around the spin tube and coupler so that it naturally mechanically couples the spin tube to the agitator shaft. When the motor/agitator shaft rotates in a first direction, the wrap spring further tightens from the neutral state to continue to couple the spin tube to the agitator shaft/coupler. Conversely, the wrap spring inherently unwinds or loosens about the spin tube and coupler when the motor reverses the torque applied to the agitator shaft, thereby resulting in the wrap spring slipping relative to the spin tube and coupler and thereby decoupling the spin tube from the agitator shaft/coupler. Thus, this type of wrap spring clutch is unidirectional as the wrap spring couples the agitator shaft and the spin tube only during rotation in one direction. Rotation of the basket is limited to rotation in only one direction, the direction that corresponds to the engagement of the clutch. Thus, it follows that when the motor is reversed to reverse the torque on the agitator shaft and brake the agitator, the wrap spring decouples the spin tube from the agitator shaft, and the spin tube and thereby the basket continue to rotate. Consequently, a separate brake that acts upon the spin tube or other component coupled to the basket is required to cease rotation of the basket. It is therefore desirable have a clutch that eliminates the need for a separate brake by coupling the motor and basket during rotation in both forward and reverse directions so that reversal of the motor brakes the basket.